cvc-complex-type.2.4.c: The matching wildcard is strict, but no declaration can be found - xsd

Question

I am trying to understand <any> element in xsd. I had two xsds.
Book Catalogue.xsd
<?xml version="1.0" encoding="ISO-8859-1"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.w3schools.com" xmlns="http://www.w3schools.com"
elementFormDefault="qualified">
<xs:element name="BookCatalogue">
<xs:complexType>
<xs:sequence>
<xs:element name="Book" maxOccurs="unbounded">
<xs:complexType>
<xs:sequence>
<xs:element name="Title" type="xs:string" />
<xs:element name="Author" type="xs:string" />
<xs:element name="Date" type="xs:string" />
<xs:element name="ISBN" type="xs:string" />
<xs:element name="Publisher" type="xs:string" />
<xs:any namespace="##any" minOccurs="0" />
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
Reviewer.xsd
<?xml version="1.0" encoding="ISO-8859-1"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.w3schools.com" xmlns="http://www.w3schools.com"
elementFormDefault="qualified">
<xs:element name="Reviewer">
<xs:complexType>
<xs:sequence>
<xs:element name="Name">
<xs:complexType>
<xs:sequence>
<xs:element name="First" type="xs:string" />
<xs:element name="Last" type="xs:string" />
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:sequence>
</xs:complexType>
</xs:element>
</xs:schema>
But if i validate the below xml based on above xsd, i am getting cvc-complex-type.2.4.c: The matching wildcard is strict, but no declaration can be found for element 'p:Reviewer'. error. Does both xsd file should not be in same namespace?
<?xml version="1.0" encoding="UTF-8"?>
<pr:BookCatalogue xmlns:pr="http://www.w3schools.com"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3schools.com AddRequest.xsd ">
<pr:Book>
<pr:Title>pr:Title</pr:Title>
<pr:Author>pr:Author</pr:Author>
<pr:Date>pr:Date</pr:Date>
<pr:ISBN>pr:ISBN</pr:ISBN>
<pr:Publisher>pr:Publisher</pr:Publisher>
<p:Reviewer xmlns:p="http://www.w3schools.com"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3schools.com Children.xsd ">
<p:Name>
<p:First>p:First</p:First>
<p:Last>p:Last</p:Last>
</p:Name>
</p:Reviewer>
</pr:Book>
</pr:BookCatalogue>

Answer 1

Two options...
Option One: If you do not want to have to have the definition of p:Reviewer present, add processContents="lax" to your xs:any element:
<xs:any namespace="##any" minOccurs="0" processContents="lax"/>
Per XML Schema Part 0: Primer Second Edition:
The lax value of the processContents attribute instructs an XML
processor to validate the element content on a can-do basis: It will
validate elements and attributes for which it can obtain schema
information, but it will not signal errors for those it cannot obtain
any schema information.
See also XML Validation in Java: processContents=“lax” seems not to work correctly.
You should also carefully adjust your xsi:schemaLocation values to point to the actual filename of each XSD for each namespace in play. Here is your XML instance with the changes that I made:
<?xml version="1.0" encoding="UTF-8"?>
<pr:BookCatalogue
xmlns:pr="http://www.w3schools.com"
xmlns:p="http://www.w3schools.com/1"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.w3schools.com BookCatalogue.xsd http://www.w3schools.com/1 Reviewer.xsd">
<pr:Book>
<pr:Title>pr:Title</pr:Title>
<pr:Author>pr:Author</pr:Author>
<pr:Date>pr:Date</pr:Date>
<pr:ISBN>pr:ISBN</pr:ISBN>
<pr:Publisher>pr:Publisher</pr:Publisher>
<p:Reviewer>
<p:Name>
<p:First>p:First</p:First>
<p:Last>p:Last</p:Last>
</p:Name>
</p:Reviewer>
</pr:Book>
</pr:BookCatalogue>
Note: Make sure that the targetNamespace in Review.xsd matches what's declared for it in BookCatalogue.xml's xsi:schemaLocation attribute.
Option Two: If you do want to insist that the definition of p:Reviewer be present, just make the above changes to be sure that Review.xsd can be found per the xsi:schemaLocation mechanism. No processContents setting is required; it defaults to strict.